Establishing Safe Zones to Avoid Nerve Injury in the Approach to the Humerus in Pediatric Patients

Abstract

Background: The surgical anatomy of upper-extremity peripheral nerves in adults has been well described as “safe zones” or specific distances from osseous landmarks. In pediatrics, relationships between nerves and osseous landmarks remain ambiguous. The goal of our study was to develop a model to accurately predict the location of the radial and axillary nerves in children to avoid iatrogenic injury when approaching the humerus in this population. Methods: We conducted a retrospective review of 116 magnetic resonance imaging (MRI) scans of entire humeri of skeletally immature patients; 53 of these studies met our inclusion criteria. Two independent observers reviewed all scans. Arm length was measured as the distance between the lateral aspect of the acromion and the lateral epicondyle. We then calculated the distances (defined as the percentage of arm length) between the radial nerve and distal osseous landmarks (the medial epicondyle, transepicondylar line, and lateral epicondyle) as well between the axillary nerve and the most lateral aspect of the acromion. Results: The axillary nerve was identified at a distance equaling 18.6% (95% confidence interval [CI], ±0.62%) of arm length inferior to the lateral edge of the acromion. The radial nerve crossed (1) the medial cortex of the posterior part of the humerus at a distance equaling 63.19% (95% CI: ±0.942%) of arm length proximal to the medial epicondyle, (2) the middle of the posterior part of the humerus at a distance equaling 53.9% (95% CI: ±1.08%) of arm length proximal to the transepicondylar line, (3) the lateral cortex of the posterior part of the humerus at a distance equaling 45% (95% CI: ±0.99%) of arm length proximal to the lateral epicondyle, and (4) from the posterior to the anterior compartment at a distance equaling 35.3% (95% CI: ±0.92%) of arm length proximal to the lateral epicondyle. A strong linear relationship between these distances and arm length was observed, with an intraclass correlation coefficient of >0.9 across all measurements. Conclusions: The positions of the radial and axillary nerves maintain linear relationships with arm lengths in growing children. The locations of these nerves in relation to palpable osseous landmarks are predictable. Clinical Relevance: Knowing the locations of upper-extremity peripheral nerves as a proportion of arm length in skeletally immature patients may help to avoid iatrogenic injuries during surgical approaches to the humerus.

Establishing safe zones to avoid nerve injury in the posterior minimally invasive plate osteosynthesis for humerus fractures: a magnetic resonance imaging study

“…Several studies have used the HL as a reference to describe the proportional distance between neurovascular structures and osseous landmarks. 2 , 8 , 11 , 20 In our study, when adjusting for the HL, the anatomic variability of AN is maintained, probably associated with a more proximal location and a shorter and perpendicular trajectory.…”

“…The anatomic relationship of the RN to the medial and lateral epicondyles and the TEA has been previously described. 11 , 20 Despite the lower variability of RN measurements in relation to the TEA, it must be considered that patients present humerus fracture, so the position of this axis will vary. In patients with comminuted fractures, the use of the TEA is limited, so its practical usefulness is limited to simple fractures that can be reduced anatomically.…”

“…Therefore, to determine the 3D distance between 2 points on an MRI, we used trigonometrical correction (Pythagoras theorem). 20 …”

Anatomic consideration of the radial nerve in relation to humeral length for unilateral external fixation: a retrospective study using magnetic resonance imaging findings in korean

“…Many imaging techniques exist, and MRI is considered as a reliable and valid means of visualizing the radial nerve [ 17 ]. Furthermore, studies using MRI have yielded reliable results [ 18 , 19 ]. On MRI, the course of the radial nerve can be traced as it traverses along the posterior arm through the triceps muscles, around the lateral humeral cortex, then through the intermuscular septum between the brachioradialis and brachialis before it branches into the posterior interosseous nerve before anteriorly drifting away from the cortex [ 20 ].…”

An Anatomic Study of the Sural Nerve Using 3-Tesla MRI: A Comparison to Cadaveric Data With Surgical Applications

“…This may slightly increase the distances of the SN to the aforementioned anatomic landmarks; however, these increases are small. Kammar et al 14 also observed a positive correlation between patient height and horizontal distance from the SN to the LBA, whereas O’Shea et al 27 noted a positive linear relationship between arm length and radial and axillary nerve positions relative to osseous landmarks. BMI also exerted a small positive effect on the distance of the SN to the LBA at 5 cm above the SAI as demonstrated by the correlation value r = 0.25 ( P <.001).…”